A short-wavelength, wide-field-of-view lens for space use

Abstract

The present invention discloses a short-wavelength, large-field-of-view lens for space use, comprising: a reverse telephoto lens group and a rear lens group coaxially arranged in sequence along the direction of light incidence; the reverse telephoto lens group comprises a first negative lens and a second negative lens arranged in sequence; the rear lens group comprises a third positive lens, a fourth positive lens, a fifth positive lens, a sixth negative lens, a seventh positive lens, and an eighth negative lens arranged in sequence. By implementing the present invention, a reverse telephoto lens group and a rear lens group are provided, wherein the reverse telephoto lens group can cause the principal plane parameters of the lens to shift backward, thereby facilitating the incidence of light into the rear lens group. At the same time, by reasonably setting the optical focal length and material thermal expansion coefficient of each lens in the two lens groups, the lens can achieve a large field of view angle and can achieve image plane stability under high and low temperature conditions of vacuum and normal pressure, meeting the requirements of aerospace miniaturization, large field of view, and long-period monitoring, and can also be used for various ground imaging needs.

Description

Technical Field

[0001] The present invention relates to the technical field of optical design, and in particular to a short-wavelength, large-field-of-view lens for space use. Background Art

[0002] Shortwave infrared imaging systems are widely used in industrial safety, particularly in power and high-temperature monitoring. However, their high cost has limited their application in space environments. However, with technological advancements, shortwave infrared imaging systems are becoming increasingly affordable, leading to their use in power system monitoring for space stations and satellite platforms.

[0003] However, due to application limitations and cost issues, few shortwave imaging cameras have wide-field-of-view, low-distortion lenses. Lenses with a field of view of 60° or more exhibit distortion greater than 5%. Furthermore, existing shortwave infrared imaging systems exhibit unstable imaging within the space station due to its unique radiation, temperature, and pressure environments, making them unusable for extended periods of time. Summary of the Invention

[0004] In view of this, an embodiment of the present invention provides a short-wavelength, large-field-of-view lens for space use to solve the technical problems of existing short-wavelength infrared imaging systems having a small field of view and unstable imaging in space.

[0005] An embodiment of the present invention provides a short-wavelength, wide-field-of-view lens for space use, comprising: a reverse telephoto lens group and a rear lens group coaxially arranged in sequence along a light incident direction; the reverse telephoto lens group comprising a first negative lens and a second negative lens arranged in sequence; and the rear lens group comprising a third positive lens, a fourth positive lens, a fifth positive lens, a sixth negative lens, a seventh positive lens, and an eighth negative lens arranged in sequence.

[0006] Furthermore, the sixth negative lens and the seventh positive lens are combined into a cemented lens.

[0007] Furthermore, the short-wavelength, wide-field-of-view lens for space use further comprises: a filter, which is arranged behind the rear lens group along the incident direction of light.

[0008] Furthermore, the short-wavelength, wide-field-of-view lens for space use further includes: an aperture, which is arranged between the fifth positive lens and the sixth negative lens.

[0009] Furthermore, the absolute value of the focal length f1 of the first negative lens satisfies the condition: 80mm<|f1|<90mm; the absolute value of the focal length f2 of the second negative lens satisfies the condition: 12mm<|f2|<13mm; the absolute value of the focal length f3 of the third positive lens satisfies the condition: 20mm<|f3|<25mm; the absolute value of the focal length f4 of the fourth positive lens satisfies the condition: 400mm<|f4|<450mm; the absolute value of the focal length f5 of the fifth positive lens satisfies the condition: 25mm<|f5|<30mm; the absolute value of the focal length f6 of the cemented lens satisfies the condition: 15mm<|f6|<20mm; the absolute value of the focal length f8 of the eighth negative lens satisfies the condition: 300mm<|f8|<320mm.

[0010] Furthermore, the material of the first negative lens is quartz glass, the thickness of the first negative lens is 3.5 mm, and the clear aperture of the first negative lens is 28 mm.

[0011] Furthermore, the second negative lens is an aspherical lens.

[0012] Furthermore, the field of view of the short-wavelength, wide-field-of-view lens for space use is 78°.

[0013] Furthermore, the absolute value of the full-field distortion of the short-wavelength, wide-field-of-view lens for space is greater than 0 and less than 5%.

[0014] Furthermore, the F number of the space short-wavelength wide-field lens is 3.

[0015] The technical solution of the present invention has the following advantages:

[0016] The short-wavelength, wide-field-of-view lens for space use provided by embodiments of the present invention utilizes a reverse telephoto lens assembly and a rear lens assembly. The reverse telephoto lens assembly shifts the lens' principal plane parameters backward, facilitating the entry of light into the rear lens assembly. Furthermore, by properly configuring the focal length and thermal expansion coefficient of each lens in the two lens assemblies, the lens achieves a wide field of view and maintains image stability under both vacuum and atmospheric pressure conditions, meeting aerospace requirements for miniaturization, a wide field of view, and long-term surveillance. It can also be used for various terrestrial imaging needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of the structure of a short-wavelength, wide-field-of-view lens for space use in an embodiment of the present invention;

[0019] FIG2( a ) is a diagram of the optical modulation transfer function of the optical system of the lens under normal temperature and pressure conditions in an embodiment of the present invention;

[0020] FIG2( b ) is a diagram of the optical modulation transfer function of the optical system of the lens under vacuum and room temperature conditions in an embodiment of the present invention;

[0021] FIG2( c ) is a diagram of the optical modulation transfer function of the optical system of the lens under vacuum and low temperature conditions of -40°C in an embodiment of the present invention;

[0022] FIG2( d ) is a diagram of the optical modulation transfer function of the optical system of the lens under vacuum and high temperature conditions of 60°C in an embodiment of the present invention;

[0023] Figure 3 is the optical system distortion curve of the lens in the embodiment of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0027] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The embodiment of the present invention provides a short-wavelength and large-field-of-view lens for space use, such as Figure 1 As shown, the short-wavelength, large-field-of-view lens for space use includes: a reverse telephoto lens group and a rear lens group coaxially arranged in sequence along the direction of light incidence; the reverse telephoto lens group includes a first negative lens 1 and a second negative lens 2 arranged in sequence; the rear lens group includes a third positive lens 3, a fourth positive lens 4, a fifth positive lens 5, a sixth negative lens 6, a seventh positive lens 7 and an eighth negative lens 8 arranged in sequence.

[0029] The short-wavelength, wide-field-of-view lens for space use provided by embodiments of the present invention utilizes a reverse telephoto lens assembly and a rear lens assembly. The reverse telephoto lens assembly shifts the lens' principal plane parameters backward, facilitating the entry of light into the rear lens assembly. Furthermore, by properly configuring the focal length and thermal expansion coefficient of each lens in the two lens assemblies, the lens achieves a wide field of view and maintains image stability under both vacuum and atmospheric pressure conditions, meeting aerospace requirements for miniaturization, a wide field of view, and long-term surveillance. It can also be used for various terrestrial imaging needs.

[0030] As an optional implementation of this embodiment of the present invention, the first negative lens 1 can be made of optical quartz glass with strong radiation resistance. The thickness of the first negative lens 1 is 3.5 mm, and the clear aperture of the first negative lens 1 is 28 mm. In addition, the other lenses in this short-wavelength, wide-field-of-view lens for space use can also be made of radiation-resistant glass, thereby improving the lens's radiation resistance and adapting it to the requirements of operation under long-term space environmental conditions.

[0031] As an optional implementation of the embodiment of the present invention, the second negative lens 2 can be an aspheric lens, and the sixth negative lens 6 and the seventh positive lens 7 are combined into a cemented lens. This allows the lens to achieve rapid contraction of the optical path, greatly reducing the size of the lens. For the second negative lens 2, its aspheric formula satisfies formula (1),

[0032]

[0033] Among them, k is the quadratic coefficient, which can be set to 0, c is the spherical coefficient, which can be set according to the absolute value of the focal length of the second negative lens, A and B are the 4th and 6th order aspheric coefficients, and r is the aperture radius position. At the same time, the aspheric coefficient A=3.6643×10 -005 , B=2.4775×10 -007 .

[0034] As an optional implementation of the embodiment of the present invention, in the short-wavelength and wide-field lens used in the space, such as Figure 1As shown, the first negative lens 1 has a first surface convex to the object side and a second surface convex to the object side; the second negative lens 2 has a first surface convex to the object side and a second surface convex to the object side; the third positive lens 3 has a first surface convex to the object side and a second surface convex to the image side; the fourth positive lens 4 has a first surface convex to the image side and a second surface convex to the image side; the fifth positive lens 5 has a first surface convex to the object side and a second surface convex to the image side; the cemented lens has a first surface convex to the object side and a second surface convex to the image side; the eighth negative lens 8 has a first surface convex to the image side and a second surface convex to the image side.

[0035] As an optional implementation manner of an embodiment of the present invention, the absolute value of the focal length f1 of the first negative lens 1 satisfies the condition: 80mm<|f1|<90mm; the absolute value of the focal length f2 of the second negative lens 2 satisfies the condition: 12mm<|f2|<13mm; the absolute value of the focal length f3 of the third positive lens 3 satisfies the condition: 20mm<|f3|<25mm; the absolute value of the focal length f4 of the fourth positive lens 4 satisfies the condition: 400mm<|f4|<450mm; the absolute value of the focal length f5 of the fifth positive lens 5 satisfies the condition: 25mm<|f5|<30mm; the absolute value of the focal length f6 of the cemented lens satisfies the condition: 15mm<|f6|<20mm; the absolute value of the focal length f8 of the eighth negative lens 8 satisfies the condition: 300mm<|f8|<320mm.

[0036] Specifically, since the focal power of a lens is the inverse of its focal length, and the thermal expansion coefficient of a lens is a material property, its corresponding coefficient is the material's refractive index, which can be indirectly determined using a defined material refractive index. Therefore, the short-wavelength, wide-field-of-view lens for space use provided by embodiments of the present invention can select the material's focal length based on the aforementioned conditional equation, while also selecting the corresponding refractive index for each lens based on actual needs through design, calculation, and analysis. This allows the lens to achieve image stability under both vacuum and atmospheric pressure conditions, both at high and low temperatures.

[0037] As an optional implementation manner of an embodiment of the present invention, the second negative lens 2 can be selected from a material with high refractive index and low dispersion, such as heavy flint glass; the third positive lens 3 can be selected from a material with high refractive index and low dispersion, such as heavy flint glass; the fourth positive lens 4 can be selected from a conventional crown material; the fifth positive lens 5 can be selected from a conventional crown material; the sixth negative lens 6 and the seventh positive lens 7 can be selected from a material with high refractive index and low dispersion, such as heavy flint glass and a conventional crown material; the eighth negative lens 8 can be selected from a material with low refractive index and high dispersion, such as a conventional crown material.

[0038] The short-wavelength, wide-field-of-view lens for space use provided by the embodiments of the present invention utilizes an aspherical second negative lens element, ensuring a compact lens design and high imaging quality. Furthermore, the distance between the center of the rear surface of the eighth negative lens element and the image plane can be set to 3 mm, ultimately resulting in a maximum outer profile of the lens measuring φ28 × 55 mm. Consequently, the short-wavelength, wide-field-of-view lens for space use provided by the embodiments of the present invention has a compact structure and a small size.

[0039] As an optional implementation of the embodiment of the present invention, Figure 1 As shown, the short-wavelength, wide-field-of-view lens for space use also includes a filter 9, which is positioned behind the rear lens assembly along the direction of incident light. When the lens is used in different application scenarios, the filter's spectral range can be adjusted as needed, allowing the short-wavelength, wide-field-of-view lens to achieve optimal imaging in any spectral range between 900nm and 1700nm.

[0040] As an optional embodiment of the present invention, the short-wavelength, wide-field-of-view lens for space photography further includes an aperture, disposed between the fifth positive lens element and the sixth negative lens element. Specifically, positioning the aperture in the middle of the rear lens group minimizes coma or astigmatism while reducing the overall size of the lens.

[0041] The short-wavelength, wide-field-of-view lens for space provided by the embodiment of the present invention can be configured to have thicker edges and center portions of each lens in the lens, taking into account the application requirements of complex environments during space transportation, so as to meet the required environmental mechanics requirements.

[0042] As an optional embodiment of the present invention, the short-wavelength, wide-field-of-view lens for space use has a field of view of 78°, a full-field distortion greater than 0 and less than 5%, and an F-number of 3. Therefore, the short-wavelength, wide-field-of-view lens for space use provided by the present invention, through the rational selection of individual lenses in the reverse telephoto lens group and the rear lens group, and by rationally setting the relevant parameters of each lens, can achieve a field of view of 78°. This lens, compared to existing lenses, can achieve wide-field-of-view monitoring. Furthermore, while maintaining this wide field of view, the full-field distortion is less than 5%, and the F-number is 3. Thus, this lens achieves low-distortion imaging with a wide field of view.

[0043] The short-wavelength, wide-field-of-view lens for space use provided by the present invention can be used in detectors with a resolution of 640×512 and a pixel size of 15μm. Furthermore, the short-wavelength, wide-field-of-view lens for space use is also backward compatible with detectors with smaller target areas and larger pixels.

[0044] The short-wavelength, wide-field-of-view lens for space use provided in an embodiment of the present invention, by setting the curvature direction and degree of each lens in the lens and setting the focal length of each lens according to the above relationship, can ensure that the angle between the main light of each field of view and the detector is no greater than 10°, ensuring that the energy drop due to the incident angle of the light is no more than 94%, and the normalized illumination of the edge field of view is 84.6%.

[0045] According to the above embodiment, the various lenses in the short-wavelength and wide-field-of-view lens for space use are arranged, and the result can be obtained as shown in Figures 2 and Figure 3 The diagram shown is a schematic diagram representing the imaging effect of the lens.

[0046] Figure 2(a) shows the optical modulation transfer function (MTF) of the lens under normal temperature and pressure conditions. The modulation transfer function (MTF) refers to the relationship between modulation and the number of line pairs per millimeter within the image, and is used to evaluate the ability to reproduce detail in a scene. Modulation is the ratio of the difference between the maximum and minimum intensities to the sum of the maximum and minimum intensities. MTF is the ratio of the image modulation to the object modulation and is a function of spatial frequency, typically expressed as 1p / mm. The modulation transfer function can be used to characterize an optical system; a larger MTF indicates better imaging quality.

[0047] Figure 2(b) shows the optical modulation transfer function of the lens under normal temperature and vacuum conditions, Figure 2(c) shows the optical modulation transfer function of the lens under low temperature and vacuum conditions at -40°C, and Figure 2(d) shows the optical modulation transfer function of the lens under low temperature and vacuum conditions at 60°C. The horizontal axis represents the spatial modulation frequency, and the vertical axis represents the optical modulation function. It can be seen that the short-wavelength, wide-field-of-view lens for space use provided by the embodiments of the present invention can maintain high imaging quality under normal temperature and pressure, vacuum conditions, -40°C vacuum conditions, and 60°C vacuum conditions.

[0048] like Figure 3 The figure below shows the distortion curve of the lens. Distortion refers to the aberration of different magnifications of different parts of an object when it is imaged through an optical system. Distortion will cause the similarity of the object and image to deteriorate. Figure 3 In the figure, the horizontal axis is the percentage of optical distortion, and the vertical axis is the field of view of the optical system. It can be seen that the distortion of this lens is less than 5%.

[0049] Although exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions, and modifications to these embodiments without departing from the spirit of the present invention and the scope of protection defined by the appended claims. Such modifications and variations fall within the scope defined by the appended claims. For other examples, those skilled in the art will readily appreciate that the order of the process steps may be varied while remaining within the scope of protection of the present invention.

[0050] Furthermore, the scope of application of the present invention is not limited to the processes, mechanisms, manufactures, compositions of matter, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of the present invention, a person of ordinary skill in the art will readily understand that any currently existing or later developed processes, mechanisms, manufactures, compositions of matter, means, methods, or steps that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein may be applied in accordance with the present invention. Therefore, the claims appended hereto are intended to include within their scope such processes, mechanisms, manufactures, compositions of matter, means, methods, or steps.

Claims

1. A short-wavelength, wide-field-of-view lens for space use, characterized in that: include: A reverse telephoto lens group and a rear lens group are coaxially arranged in sequence along the incident direction of the light; The reverse telephoto lens assembly comprises a first negative lens and a second negative lens arranged in sequence; The rear lens group includes a third positive lens, a fourth positive lens, a fifth positive lens, a sixth negative lens, a seventh positive lens and an eighth negative lens arranged in sequence; The sixth negative lens and the seventh positive lens are combined into a cemented lens; The lens further comprises: a filter, which is arranged behind the rear lens group along the incident direction of the light; The lens further includes: an aperture, the aperture being disposed between the fifth positive lens and the sixth negative lens; The absolute value of the focal length f1 of the first negative lens satisfies the condition: 80 mm < | f1 | < 90 mm; The absolute value of the focal length f2 of the second negative lens satisfies the condition: 12 mm < |f2| < 13 mm; The absolute value of the focal length f3 of the third positive lens satisfies the condition: 20 mm < | f3 | < 25 mm; The absolute value of the focal length f4 of the fourth positive lens satisfies the condition: 400 mm < |f4| < 450 mm; The absolute value of the focal length f5 of the fifth positive lens satisfies the condition: 25 mm < |f5| < 30 mm; The absolute value of the focal length f6 of the cemented lens satisfies the condition: 15mm<|f6|<20mm; The absolute value of the focal length f8 of the eighth negative lens satisfies the condition: 300 mm < |f8| < 320 mm; The material of the first negative lens is quartz glass, the thickness of the first negative lens is 3.5 mm, and the clear aperture of the first negative lens is 28 mm; The second negative lens is an aspherical lens; It is characterized in that the field of view angle of the short-wavelength wide-field lens for space use is 78°; The absolute value of the full field of view distortion of the short-wavelength, wide-field-of-view lens for space use is greater than 0 and less than 5%; The F number of the short-wavelength, wide-field lens for the space is 3.

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